Blood Parasites in Sympatric Vultures: Role of Nesting Habits and Effects on Body Condition.

Guillermo Blanco,Nayden Chakarov

doi:10.3390/ijerph18052431

Abstract

Avian haemosporidians are a common and widespread group of vector-borne parasites capable of infecting most bird species around the world. They can negatively affect host condition and fitness. Vultures are assumed to have a very low prevalence of these blood parasites, likely due to their strong immunity; however, factors contributing to variation in host exposure and susceptibility to haemosporidians are complex, and supporting evidence is still very limited. We analyzed blood samples collected from nestlings of three vulture species in Spain over 18 years, and used updated nested-PCR protocols capable of detecting all haesmosporidian cytochrome b lineages typical for diurnal birds of prey (Accipitriformes). Similarly to previous studies, we found low haemosporidian prevalence in cliff-breeding species, with Leucocytozoon as the only represented blood parasite genus: 3.1% in griffon vultures (Gyps fulvus) (n = 128) and 5.3% in Egyptian vultures (Neophron percnopterus) (n = 114). In contrast, the tree-breeding cinereous vulture (Aegypius monachus) had a substantially higher prevalence: 10.3% (n = 146). By far the most common lineage in Spanish scavenging raptors was the Leucocytozoon lineage CIAE02. No effects of nestling age and sex, or temporal trends in prevalence were found, but an effect of nest habitat (tree-nest vs. cliff-nest) was found in the griffon vulture. These patterns may be explained by a preference of vectors to forage in and around trees rather than on cliffs and wide open spaces. We found an apparent detrimental effect of haemosporidians on body mass of nestling cinereous vultures. Further research is needed to evaluate the pathogenicity of each haemosporidian lineage and their interaction with the immune system of nestlings, especially if compromised due to pollution with pharmaceuticals and infection by bacterial and mycotic pathogens.

Highlights

Avian scavengers play a key functional role in ecosystems, in landscapes shaped by extensive animal husbandry [1,2,3]
In support of the nesting habitat hypothesis, we found that the prevalence of haemosporidians in nestling griffon vultures was lower in cliff-nests, which form the bulk in the population, than in nests built by cinereous vultures in maritime pines
We found a negative correlation of haemosporidian infection with body mass of nestling cinereous vultures from loose breeding colonies in pinewoods, but not in colonial cliffand tree-nesting griffon vultures or territorial Egyptian vultures exclusively nesting in cliffs

Summary

Introduction

Avian scavengers play a key functional role in ecosystems, in landscapes shaped by extensive animal husbandry [1,2,3]. Scavengers may be subject to strong anthropogenic impacts, but the estimation of their magnitude can be hindered by insufficient baseline data. This may be the case with information about the blood parasites of vultures. Haemosporidian parasites of vultures have been described only through microscopic analyses, which may underestimate their diversity and prevalence. Haemosporidian parasites of the genera Plasmodium, Haemoproteus, and Leucocytozoon commonly infect birds of all major phylogenetic branches worldwide [4]. PCR-based methods for the detection and discrimination of avian blood parasites have shown to be complementary to microscopic methods, increasing the sensitivity for low-intensity infections and differentiating better between taxa. All haemosporidian parasites are transmitted by blood-sucking vectors, which crucially determine

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